Obesity is known to increase the risk of getting breast cancer, but now researchers find that the extra weight can make the battle even tougher for some women, despite receiving optimal treatment for their disease.

Dr. Joseph Sparano of the Albert Einstein College of Medicine’s Montefiore Medical Center and colleagues analyzed date on 6,885 breast cancer patients enrolled in three National Cancer Institute (NCI)-sponsored trials. Only women with stage 1, 2 or 3 breast cancer were considered for the analysis. The women in the study had normal heart, kidney, liver and bone marrow function and were considered overall healthy. The patients were followed for eight years.

Having a higher body mass index (BMI) was found to be associated with a higher risk of breast cancer recurrence and death especially among women with estrogen receptor positive breast cancer, the most common form of the disease affecting two-thirds of all patients in the United States and worldwide.

“We found that obesity at diagnosis of breast cancer is associated with about a 30 percent higher risk of recurrence and a nearly 50 percent higher risk of death despite optimal treatment (such as chemotherapy and hormonal therapy),” said Dr. Sparano.

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The authors suggest three theories for the association. First, women with greater fat stores produce more estrogen which may fuel the growth of hormone receptor positive tumors. Second, heavier people are more likely to be insulin-resistant which may also trigger the growth of cancerous cells. Lastly, excess body fat may cause more inflammation in the body which could be a factor in the recurrence or spreading of cancer cells.

“There are several possibilities and it could be any one of these factors or a combination of a few,” says Sparano.

When cancer patients are undergoing treatment, one of the goals for many patients is to avoid weight loss associated with the decreased appetite due to either the disease or side effects from therapy. Malnutrition can interrupt a patient’s ability to keep body tissue healthy and fight infection.

Instead, dietitians and physicians should individualize a plan for cancer patients to help them strive for a more healthful balance, including a varied diet with adequate calories to promote a slow and steady weight reduction while maintaining appropriate nutritional needs and an exercise program suitable for the patient.

The chance of getting breast cancer in one’s lifetime is 1 in 8 with about 15% of woman under the age of 45 being diagnosed. There has been a lot of debate over the efficacy of thermograms versus mammograms, but today there is more research on diagnostic tools. What must be understood are the differences between the two tests.